My invention relates to a transmission of the kind that I have disclosed in my copending patent application, Ser. No. 951,279 entitled "Multiple Ratio Manual Transmission" filed Sep. 25, 1992. My copending patent application is assigned to the assignee of my present invention. Reference may be made to the copending disclosure to supplement the description of my present invention.
A manual transmission of the kind disclosed in my copending application and other transmissions presently known in the art as illustrated in U.S. Pat. Nos. 4,222,281 and 4,799,399 comprise an input shaft, a mainshaft and a countershaft. The mainshaft and the countershaft respectively support torque transmitting gearing and cluster gear assembly gear elements. Synchronizer clutches are used to establish selectively each of several forward driving torque flow paths and at least a single reverse torque flow path. A driver operator shift lever is mounted on the transmission housing that encloses the mainshaft gears and the cluster gear assembly gear elements. The synchronizer clutches include clutch sleeves that are adapted to be shifted axially to establish and disestablish the torque flow paths.
A linkage mechanism for actuating the shift sleeves includes a shift fork for each sleeve. A mechanical connection is established between the driver-controlled shift lever and the individual shift forks by extensions or selector plates carried by each shift fork. The shift lever can be rotated in a plane transverse to the axis of the mainshaft or moved fore and aft in a plane parallel to the axis of the mainshaft as a mechanical connection is established and disestablished between the shift lever and the individual shift plates.
It is common practice in the prior art to provide a shift fork interlock that prevents shifting movement of one shift fork as a companion shift fork is selected by the driver and actuated as the driver shifts the shift lever in one direction or the other. An offset lever connected to one end of the shift lever is rotated or shifted axially by the shift lever as the selector plates and shift forks are selected by the operator. The shift forks may be mounted on and supported by a common shift rail arranged in parallel disposition with respect to the axis of the mainshaft.
In prior art constructions, it is usual practice to provide a motion controlling gate secured to the transmission housing. This establishes a motion pattern for the offset lever and the shift lever as the driver establishes and disestablishes the various transmission ratios. It also is common practice to mount the interlock mechanism on a stationary portion of the transmission independently of the mounting structure for the shift lever. Such arrangements introduce assembly problems because of the complexity of the shift linkage. Further, design tolerances that normally are associated in the design and manufacture of the transmission and the linkage mechanism introduce calibration errors that have the potential for misaligning the selector mechanism for the selector plates and for mislocating the synchronizer clutch sleeves.